So, if i have Foo instance named "Foo1" that belong to city numbered 1 and have another Foo instance named "Foo1" that also belongs to city no 1 how I can glue it up if they both have DIFFERENTS Bars to one Foo instance that will be include all that Bars?

module Merge
# True if self is safe to merge with +object+, ie they are more or less equal.
# Default implementation compares all attributes except id and metadata.
# Can be overridden in specific models that have a neater way of comparison.
def merge_equal?(object)
object.instance_of?(self.class) and merge_attributes == object.merge_attributes
end
MERGE_INDIFFERENT_ATTRIBUTES = %w(id created_at updated_at).freeze
MERGE_EXCLUDE_ASSOCIATIONS = [].freeze
# Attribute hash used for comparison.
def merge_attributes
merge_attribute_names.inject({}) do |attrs, name|
attrs[name] = self[name]
attrs
end
end
# Names of the attributes that should be merged.
def merge_attribute_names
attribute_names - MERGE_INDIFFERENT_ATTRIBUTES
end
# Names of associations excluded from the merge.
# Override if the model has multiple scoped associations,
# that can all be retrieved by a single has_many association.
def merge_exclude_associations
MERGE_EXCLUDE_ASSOCIATIONS
end
# Merge this object with the given +objects+.
# This object will serve as the master,
# blank attributes will be taken from the given objects, in order.
# All associations to +objects+ will be assigned to +self+.
def merge!(*objects)
transaction do
merge_attributes!(*objects)
merge_association_reflections.each do |r|
local = send(r.name)
objects.each do |object|
if r.macro == :has_one
other = object.send(r.name)
if local and other
local.merge!(other)
elsif other
send("#{r.name}=", other)
end
else
other = object.send(r.name) - local
# May be better to compare without the primary key attribute instead of setting it.
other.each {|o| o[r.foreign_key] = self.id}
other.reject! {|o| local.any? {|l| merge_if_equal(l,o) }}
local << other
end
end
end
objects.each {|o| o.reload and o.destroy unless o.new_record?}
end
end
def merge_attributes!(*objects)
blank_attributes = merge_attribute_names.select {|att| self[att].blank?}
until blank_attributes.empty? or objects.empty?
object = objects.shift
blank_attributes.reject! do |att|
if val = object[att] and not val.blank?
self[att] = val
end
end
end
save!
end
private
def merge_association_reflections
self.class.reflect_on_all_associations.select do |r|
[:has_many, :has_one, :has_and_belongs_to_many].include?(r.macro) and
not r.options[:through] and
not merge_exclude_associations.include?(r.name.to_sym)
end
end
def merge_if_equal(master, object)
if master.merge_equal?(object)
master.merge!(object) ; true
end
end
end
ActiveRecord::Base.class_eval { include Merge }
# Compatibility with ActiveRecord 2.x
class ActiveRecord::Reflection::AssociationReflection
alias :foreign_key :primary_key_name unless method_defined? :foreign_key
end